Code crashes with segfault about hvm HOT 12 CLOSED

Those examples are incomplete, you have to follow the link on the top of each table.

Will add something to make this clear.

from hvm.

I see. Still, I believe that even the incomplete example should not segfault ... ;)

from hvm.

even the incomplete example should not segfault

Oh, you are right! This should be investigated.

I guess that is allocating nodes ad infinitum. A better allocator is needed, indeed, as per #38 .

from hvm.

Yes, finding where this (and any other) segfault comes from is very important so we can put the right checks and error handlers in place. Thanks for the issue.

from hvm.

@01mf02 I'm not able to reproduce the segfault. I'm also using commit 1da2875. Just to be clear, are you compiling the whole contents of this file, or just the incomplete snippet from the README? I don't think the incomplete snippet would work, as it's missing some definitions, e.g. App, right? Here's what I did:

bash-5.1$ git rev-parse HEAD
1da287553156dae87b23e1170575af7d73c4531c
bash-5.1$ nix build
bash-5.1$ cd bench/LambdaArithmetic/
bash-5.1$ ../../result/bin/hvm c main.hvm
Compiled to 'main.c'.
bash-5.1$ clang -O2 main.c -o main -lpthread
bash-5.1$ ./main 25
Rewrites: 65483 (0.38 MR/s).
Mem.Size: 78118 words.

822584320
bash-5.1$

from hvm.

@nothingnesses: Ok, so here is what I did: I installed HVM with cargo install --git https://github.com/Kindelia/HVM and then made a main.hvm that contains precisely the code I posted in my original post; that is, the incomplete snippet from the README. Then I used hvm c main && clang -O2 main.c -o main -lpthread to compile. Following this, ./main 25 gives the mentioned segfault.

By the way, the interpreter (?) also crashes on the same file, but with a stack overflow:

$ hvm r main 5
Reducing.

thread 'main' has overflowed its stack
fatal runtime error: stack overflow
Aborted (core dumped)

from hvm.

Main = λ(Main) throws a stack overflow for me in the "interpreter". I think these two stack overflows might be related

from hvm.

Main = λ(Main) throws a stack overflow because it is an infinite expression! HVM finishes stringification before printing, can't print infinite terms (yet). It would be cool if it printed lazily, like GHC, though.

from hvm.

This has the rather confusing consequence that forgetting to apply a lambda that calls a recursive constructor with an end-case throws a stack overflow

(Q 0) = HelloWorld
(Q a) = (Q (- a 1))
Lambda = λa(Q (- a 1))
Main = ((Lambda) 1) // => (HelloWorld)
Main = ((Lambda)) // => [stack overflow]

from hvm.

Yes, I'm aware. I'm already working on a higher-level, statically typed language that compiles to HVM, which will solve these issues too!

from hvm.

Main = λ(Main) throws a stack overflow because it is an infinite expression! HVM finishes stringification before printing, can't print infinite terms (yet). It would be cool if it printed lazily, like GHC, though.

So readback is the function that is crashing?

I'm getting similar issues (#151), but the problem seems to be in the ffi_normal function (the second debug never fires):

https://github.com/Kindelia/HVM/blob/71065d3bcd3d33c4b7a38ec69cb98598ae36d5f0/src/runtime.c#L1440-L1442

from hvm.

Should be working on master. If the problem is still present, please reopen the issue.

from hvm.